The objective of the proposed research is to qualitate the interactions of the control proteins of skeletal muscle in terms of enthalpy as measured in a reaction calorimeter. The results will serve as the basis for choosing between the utility of the steric model or the complexity of an allosteric model for future studies. The study should provide the first quantitative description of the interactions in these control proteins and how they are changed when Ca++ is bound to troponin. Thus our understanding of molecular events of the control of muscle contraction should be increased.